This patient should undergo transesophageal echocardiography (TEE). He has evidence of a new conduction defect on electrocardiogram suggesting a possible perivalvular abscess complicating Staphylococcus aureus infective endocarditis. Perivalvular abscesses may be present in 30% to 40% of patients with infective endocarditis, and the risk may be further increased in those with a bicuspid aortic valve. The diagnosis should be considered in patients with persistent bacteremia, fever, or evidence of conduction system disorders who are being treated with appropriate antibiotic therapy. TEE has a high sensitivity and specificity for identifying perivalvular extension of infection and is the diagnostic study of choice when a perivalvular abscess is suspected.

Cardiac CT has not been extensively studied for use in diagnosing myocardial infection and is not typically used for this purpose. Cardiac magnetic resonance (CMR) imaging, however, is effective in identifying intramyocardial infection, although it is a more complex technology that may have limited availability in some areas. CMR imaging is often used in situations in which a perivalvular abscess is suspected but transesophageal echocardiography is equivocal.

Evidence of a conduction system disorder may be the only indicator of a perivalvular abscess in a patient otherwise responding clinically to treatment for infective endocarditis, as in this patient. Because of the significance of this possible complication, failure to further evaluate conduction system abnormalities in this setting would be inappropriate.

Although transthoracic echocardiography is effective for initial evaluation for endocarditis and assessing for potential complications once endocarditis has been diagnosed (such as valvular or left ventricular dysfunction), TEE is significantly more sensitive for detecting perivalvular abscess because of the closer proximity of the ultrasound probe to the valve structures. It is therefore preferred to transthoracic echocardiography if this diagnosis is a consideration.